Deltoid muscle of the arm. The deltoid muscle is the site most typically used for vaccines. However, this site is not common for self-injection because its small muscle mass limits the volume of.

Acts mainly as an abductor of the shoulder and stabiliser of the humeral head. as well as assists in forward elevation. The deltoid is a very powerful muscle and is used in many ADLs (eg putting clothes online, carrying shopping bags, washing hair) and many athletic activities. (eg netball, swimming, water polo).